W1307 (Revised)

Houndstongue (Cynoglossum officinaleL.) Identification and Control a STOPSTOP THETHE SPREADSPREAD

Rodney G. Lym NDSU Department of Plant Sciences

Houndstongue is a biennial poisonous herb that is native to Eurasia. The plant is a member of the Borage family, which includes more commonly known plants such as Virginia Bluebells, Forget Me Nots and the fiddlenecks. Houndstongue commonly is found in disturbed areas, including roadsides and trails, and in pasture and woodlands following soil disturbance or overgrazing. How do I identify this plant? The leaves are oblong, b very pubescent and rough, which resembles a hound’s tongue (Figure 1). Plants bolt during early summer the second year of Figure 1. Houndstongue is a biennial that growth to a height of 1 to 4 feet and flower in mid-June (Figure overwinters as a rosette during the first year 2a). Flowers clusters range from red to burgundy (Figure 2b). of growth (a). The plant has very pubescent leaves that feel like a dog’s tongue, hence Each flower produces three to four nutlets (Figure 3a), which the common name (b). are flat and teardrop-shaped with a very hard seed coat and numerous barbs (Figure 3b). What is houndstongue’s growth cycle? Houndstongue forms a rosette the first year of growth (Figure 1a) and bolts and flowers the second season. The plant only Figure 2. Houndstongue bolts reproduces from seed, but it early in the summer during the can spread great distances second season of growth and because the barbs on the produces small red to burgandy nutlets cling to clothing, flowers (a). The flowers are machinery and animals. Plants inconspicuous and bloom in generally are found along series for several weeks (b). trails and roadsides, on the edge of wooded areas and in disturbed habitats.

North Dakota Agricultural Experiment Station NDSU Extension Service a b Fargo, North Dakota April 2018 Why is this plant a concern? Houndstongue tends to be a nuisance plant rather than a noxious weed unless infestations grow to become large patches. The nutlets often become imbed- ded in the wool or hair of livestock, which can cause a loss in the value of the wool and/or increase costs to remove the burrs. Eye damage can occur if burrs become embedded in the eye or eye- lids. The burrs can be problematic for hikers, hunters and fisher- men, and also to their pets. a Houndstongue contains alkaloids that are especially toxic to cattle and horses. The plant rarely is eaten in the green state; however, animals will eat the dried plant in hay. Sheep are more resistant to the pyrrolizidine alkaloids than other livestock, while horses, espe- cially when confined to small areas infested with houndstongue, are more likely to ingest toxic levels. Fatal liver disease in horses occurred following two weeks of feeding hay with as little as 6 percent houndstongue. Where in the state is this plant found? The plant first was collected in North Dakota near Valley City in 1911, and in 1950, it was described by O.A. Stevens of the North Dakota Agricultural College as confined to “Ransom, Barnes, and Steele Counties only.” Beginning in the late1990s and early 2000s, houndstongue began to be more widespread in North Dakota, especially in the b southwestern and north-central part of the state. How do I control this plant? Prevention is the best method Figure 3. Three to four nutlets form from to keep houndstongue from invading North Dakota. Use only each houndstongue flower (a). The seeds certified weed-free hay and eradicate new infestations before the have numerous barbs which can attach to plant can spread. Escort (metsulfuron) at 1 to 2 ounces per acre people, animals, and equipment helping the plant spread to new areas (b). (oz/A) is very effective for controlling houndstongue and can be applied throughout the growing season. First-year houndstongue rosettes can be controlled with 2,4-D at 2 pints/A applied from late May to mid-June. Second-year plants are much less susceptible to 2,4-D. Plateau applied at 8 to 12 oz/A will control houndstongue pre- and postemergence, but grass injury, especially to the cool-season species, is likely when Plateau is applied at the maximum rate. A root weevil, Mogulones cruciger, has been released for control of houndstongue in Canada. The insect has become well- established in Alberta and has greatly reduced the houndstongue If you find this weed, infestation in that province. Although this biocontrol agent has report it to your not been cleared for release in the United States, M. cruciger local weed officer. establishment has been documented in Montana, Idaho and Washington and it is very likely the insect eventually will be found HELP STOP THE in North Dakota. The seed-feeding weevil M. borraginis is in the final stages of SPREAD evaluation as a likely candidate for release. No other biocontrol agents are under consideration for release on houndstongue. All photographs by Rodney G. Lym. For more information on this and other topics, see www.ag.ndsu.edu The NDSU Extension Service does not endorse commercial products or companies even though reference may be made to tradenames, trademarks or service names. NDSU encourages you to use and share this content, but please do so under the conditions of our Creative Commons license. You may copy, distribute, transmit and adapt this work as long as you give full attribution, don’t use the work for commercial purposes and share your resulting work similarly. For more information, visit www.ag.ndsu.edu/agcomm/creative-commons. County commissions, North Dakota State University and U.S. Department of Agriculture cooperating. NDSU does not discriminate in its programs and activities on the basis of age, color, gender expression/identity, genetic information, marital status, national origin, participation in lawful off-campus activity, physical or mental disability, pregnancy, public assistance status, race, religion, sex, sexual orientation, spousal relationship to current employee, or veteran status, as applicable. Direct inquiries to Vice Provost for Title IX/ADA Coordinator, Old Main 201, NDSU Main Campus, 701-231-7708, [email protected]. This publication will be made available in alternative formats for people with disabilities upon request, 701-231-7881. 3M-2-06